Trolley wheel



June 10, 1930. w, F GRAHAM 1,763,303

TROLLEY WHEEL Filed Nov. 14, 1928 Inventof M41: TEE F GRAHA r Attorneysliding shoe,

w without regard to Patented June 10, 1930 UNITED STATES PATENT OFFICEWALTER F. GRAHAM,

OF MANSFIELD, OHIO, A CORPORATION OF NEW JERSEY 'rnoLLEY WHEEL Myinvention relates to current collectors used. in moving vehicles inparticular.

The object of my current collector such as a trolley wheel or and theprocess of manufacture.

A moving current collector such as a trolley wheel or sliding shoe bymeans of which current is collected from the trolley wire for use inpropelling a moving vehicle, isrequired to meet very severe conditionsand the life and efliciency of the presentdevices are not all that mightbe desired.

Wheels and shoes can be made of forged or rolled commercially purecopper and from the standpoint of conductivity alone would be the bestmaterial that could possibly be used commercially, but such deviceswould be very expensive to make and their life would not be sufficientlyprolonged over the life of the present copper alloys to warrant theincreased expense of forging the wheel of pure copper as compared with acast alloy collector.

A wheel might be produced from cast copper but this would have itsdisadvantages in manufacturing and in order to overcome some of theobjections to the use of pure copper in the manufacture of the wheel,ingredients might be added such as lead in .smallquantities to assistthe machining and casting and also fluxes might be added, but thesewould have a decided detrimental effect upon the physical properties ofthe wheel which would render the wheel unsatisfactory for the purposeintended The material in the present wheels or shoes is ordinary brassor bronze, alloyed with lead, tin, zinc, etc., in an attempt to producea wheel which has primarily increased hardness over that of pure copperin order to increase the life of the device, but the electricalconductivity. The present collectors are not entirely satisfactory evenas to wearing quality and this is largely due to the fact that thesemetals and the foundry manipulation thereof produces a high electricalresistance alloy without an increase in hardness and strength to theextent desired, and in the device cause increased burning due to arcingbetween the that is, copper exceedingly minute form.

Application filed November 14, 1928. Serial No. 319,366.

collector and the wire as the collector slides or rolls along the-wire.invention is to provide a 7 Further, as the use of the present type ofwheel or shoe continues, groove becomes pitted more and more and thiscauses increased arcing and the life curve of the device drops off veryrapidly and also the wear upon the trolley wire is increased. It is notuncommon to find wheels in which the groove has been reduced in depth,or, in other words, metal has been collected from the trolley wire anddeposited in the groove.

To reduce the amount of wear on a collector of. the sliding type, somesuch devices are now made of special alloy steels, hardened andpolished, but such devices are of high electrical resistance and tend toare badly.

All of the above conditions are very undesirable, both for mechanicaland electrical reasons.

It is my desire to construct a collector which will be an improvementover the present wheels or shoes and it is possible to do this by usingin their manufacture certain alloys which have properties differing fromthe properties of those alloys now used in current collectors, forexample, I find it is possible to use an alloy which is composed largelyof copper and which contains in addition thereto, nickel up to about 8%and silicon up to about 2%, in the-approximate ratio of about 4 to 1. Analloy composed of the above elements when cast into a trolley wheel, asshown in Figs. 1 and 2, which are respectively a side view and an edgeview in partial section, produces a wheel in which the-nickel andsilicon may be found in different conditions; in one condition Ni Si maybe precipitated in an This precipitate of Ni Si increases moreparticularly the hardness and structure of the composition but does notaffect materially the electrical conductivity and is a non-solublecompound in a solid state, the copper forming as it were a matrix.

I find that if a wheel made of the above elements is now heated to anelevated tem perature, for example, to about 1500 to 1700 degrees F. forapproximately one quarter hour and then quenched in water toroom thesurface of the temperature, that such treatment renders the wheel quiteuniform in structure as the nickel and silicon are uniformly dispersedand in a state of solid solution.

I also find that if a wheel so made is allowed to set for a period oftime, that a change takes place in that the nickel and silicon, having astrong afiinity 'for each other, unite and form nickel silicide, N i Si,whichis a stable compound and precipitated out in the matrix. Thisprecipitated compound I find produces a hardness in the metal which wasnot there when the wheel was first cast with the nickel and silicon in astate of solid solution, and I also find that the longer the wheel setsor ages, the greater the segregation and the harder the piece becomes. Ifurther find that b heating the wheel up to a temperature of a out 450F. for about four hours and allowing it to cool, this segregation orprecipitation of the nickel sillcide or ageing can be hastened andpractically all the nickel and silicon precipitated by varying the timeand temperature to suit conditions.

I find that a wheel made and treated as above described, will have aBrinell hardness of about 150 and over as compared with about 80 beforethe ageing treatment, and the spe cific electrical resistance of thealloy per cubic centimeter will be less than in standard Wheel alloys.The normal Brinell hardness of cast copper is about 35 while that of astandard trolley wheel bronze now in use is about 60.

I further find that if after the casting has solidified and cooled toabout 1500 to 1700 degrees F., is then taken from the mould and plungedin water, that the constituents will then be uniformly distributedthroughout the mass and it is only necessary then to heat the mass up tohasten the ageing process as before stated, thus avoiding a reheating ofthe castings to 1500 to 17 00 degrees F. as before explained.

The precipitated N i Si appears to have produced the above hardnessreferred to by obstructing or offering resistance to the movement of theslip planes. This theory of the hardenin of metals is set forth anddiscussed in J eries & Archer treatise entitled Science of Metals.

y improvement in current collecting devices may be effected by the useof the said alloy of copper, nickel and silicon but I do not limitmyself to its use alone as other alloying metals than nickel may beadded to copper, such as chromium, cobalt and iron, and produce the sameor similar. effect, name ly, to precipitate in the copper matrix in thesolid state in the form of a non-soluble stable compound. The effectproduced by the use of 1% to 4% of chromium in place of the nickelreferred to above is similar to the effect pro duced by the use of 1% to4% of iron in that the strength and wearing properties of a currentcollecting device made of such material is increased. Ferro-chromiumcontaining 1% to 3% of iron may also be used to the extent of about 1%to 4% and like results secured as given above.

To produce a wheel or slider, a cavity is provided in a sand mould bythe use of a pattern, as is Well known and common practice in thefoundry art, or a permanent mould of graphite, etc., may be used. Theingredients to produce the alloy as set forth above are weighed out andbrought to a fluid condition in a graphite crucible or other means andmixed. The molten alloy is then cast in the mold, producing a device inthe rough. This casting is then machined and, if a wheel, the center ispossibly bored to fit a bushing or axle and the groove machined to size,or the casting may first be homogenized by heating to about 1500 to 1700 degrees F. and then quenched. and quenching, then such step orstepsare carried out after machining. After the machining and homogenizing,the casting is heated to about 450 F. for about four hours or to suchother predetermined temperature for such predetermined time as to givethe results desired and allowed to cool. This produces a device whichhas higher electrical conductivity and greater strength and hardnessthan the devices now in general use.

It will be seen that I have produced a wheel from a cast alloy which maybe composed of copper of about 95%, nickel 4% and silicon 1%, or by theuse of equivalent elements, and by proper heat treatment, the wheel willhave a reasonably pure copper matrix which has uniformly precipitatedtherein about 4% to 5% of Ni b i which imparts to the alloy a hardnessof a very considerable degree, and, therefore, a Wheel which possesses ahigh degree of electrical conductivity and greater hardness andstrength, giving the two properties most desirable in a trolley Wheel orsliding shoe.

I find, however, that in casting a Wheel of the above alloy thatpractical diificulties are met with, particularly shrinkage cavitiesunless very large risers are used, or such difliculties can be overcomeby replacing in the above alloy about 15% of the copper content withzinc, giving an alloy of copper 81%, zinc 15%, nickel 3% and silicon 1%.This alloy is subjected to the same heat treatments as given above butthe conductivlty is sacrificed to a degree in order to modify theworking properties of metal.

The procedure in using this modified alloy to secure a wheel casting isthe same as that for the zinc-free alloy given above.

I find that I can add to the copper, nickel and silicon mixture, zinc toreplace the copper to the extent of 38% of the copper, and it will berecognized by those skilled in the art that copper containing up to 38%zinc is what is knownin the art as alpha brass in If machined beforeheating,

I which the zinc and copper forms a solid solu- 7 tion.

In forming the above alloys of copper, nickel and silicon, either with'or without zinc, I use about four parts of nickel to one of silicon andwith this proportion the nickel and silicon combine to form the Ni Siwith very little nickel or silicon uncombined.

I also find that nickel can be substituted for the zinc and securethereby the benefits of the zinc, and this can he brought about byaddinfi to the molten mass nickel in ex- 'cessfof that which is requiredto combine "with the silicon present, thereby leaving an amount ofnickel which has notbeen used to produce the lfli sikandwhich,therefore, is held in solid solution with the copperfthe same as thezinc.

I further find that such non-soluble stable carbides, as of chromium,will produce the hardening efl'ect described above as produced bycertain silicides. Those skilled in the art will recognize from ,theabove disclosure that I haveproduced a current collector composed ofamen-ferrous alloy of copper or brass, containing a plurality of metalshaving a strong afiinity for each other and precipitating out of themass after cooling, invery fine particles in the form of a stable,non-soluble compound which will increase the hardness and strength ofthe copper or brass alloy and if-the said plurality of metals is nickeland silicon, the stable, non-soluble compound will be Ni Si.

Modifications may be made by those skilled in the art based on thedisclosure above, but I wish to be limited only by my -claim.

I claimz- 1 X The method of manufacturlng a, current collectorcomprising forming a bodycasting from a molten mixture of cop er 80%,zinc 15%, nickel 4%, silicon 1%, to the shape thesame. \r' i Intestimony whereofl aflix, my signature.

desired in a mold, then heating the casting to about 1500-de'g. F. .and'quench to about room temperature to uniformly distribute the elementsthroughout the mass and then heat the mass to about 450 deg; F. and coolslowly to precipitate the nickel and silicon as a non-soluble, stablecompound uniformly distributed throughoiitthe mass to harden WALTER F.SGIRAHAM; a

